| Thomas Morris Limited | Real estate | 2002 |
| Thomas R Dixon & Co LLP | | 2008 |
| Thomas Robin Associates Limited | Real estate | 2020 |
| Thompson Bros (South Shields) Limited | Wholesale & retail | 1936 |
| Thompson Build Ltd | Construction | 2024 |
| Thompson Health and Safety Limited | Public administration | 2019 |
| Thompson Joint Integrity Limited | Manufacturing | 2019 |
| Thompson Joint Integrity Solutions Ltd | Manufacturing | 2016 |
| Thompson Security Solutions Ltd | Administrative & support | 2016 |
| Thompson's International Tubing Services Ltd | Mining & quarrying | 2009 |
| Thomson Bros (Newcastle) Limited | Other services | 1933 |
| Thomson Properties (NE) Limited | Real estate | 2025 |
| Thomson Properties North East LLP | | 2018 |
| Thorburn Bros Limited | Wholesale & retail | 2018 |
| Thorburn's Yard Management Company Limited | Real estate | 2013 |
| Thorneygrove Limited | Wholesale & retail | 1993 |
| Thornlea Court Management Limited | Real estate | 2007 |
| Thornleigh Management Limited | Real estate | 2026 |
| Thornley & Co Landscaping and Maintenance Ltd | Administrative & support | 2024 |
| Thornley Hall Events Ltd | Arts & recreation | 2024 |
| Thorpe Anaesthesia Ltd | Health & social care | 2026 |
| Thorpes of Gosforth Limited | Wholesale & retail | 1950 |
| Thorping Woodworks Limited | Construction | 2025 |
| Thorston Ltd | Wholesale & retail | 2026 |
| Those That Know Limited | Wholesale & retail | 2021 |
| Thpd Services Ltd | Manufacturing | 2020 |
| Thread Theory UK PVT Ltd | Wholesale & retail | 2025 |
| Thredspan Limited | Information & communication | 2026 |
| Three Developments NE Ltd | Construction | 2019 |
| Three Digital Consulting Ltd | Professional & scientific | 2022 |
| Three Geese Facilities Maintenance Limited | Administrative & support | 2022 |
| Three Mile Court Management Limited | Extraterritorial | 1992 |
| Three Mile Solutions Limited | Other services | 2020 |
| Three Ports Group Ltd | Construction | 2025 |
| Three Strand Coaching Ltd | Administrative & support | 2026 |
| Threeaf (NE) Ltd | Real estate | 2019 |
| Threeday Group Ltd | Professional & scientific | 2020 |
| Thrive & Bridge Recruitment Consultants Ltd | Administrative & support | 2025 |
| Thrive and Flow Ltd | Arts & recreation | 2025 |
| Thrive Care & Support Ltd | Health & social care | 2025 |
| Thrive Drive Initiative CIC | Education | 2023 |
| Thrive in Life North East and UK Ltd | Professional & scientific | 2024 |
| Thrive Physiotherapy & Wellness Limited | Health & social care | 2026 |
| Thrivewell Medical Ltd | Professional & scientific | 2026 |
| Thrivewell Services Ltd | Wholesale & retail | 2026 |
| Thriving Alone CIC | Education | 2024 |
| Throckley Community Hall Limited | Health & social care | 1984 |
| Throckley Grill House Ltd | Hospitality | 2024 |
| Throckley Marsh Farm Ltd | Construction | 2018 |
| Throckley Motorcycles Ltd | Wholesale & retail | 2025 |
| Throckley North Management Company Limited | Real estate | 2018 |
| Throckley Property Services Ltd | Real estate | 2026 |
| Throckley Shop Ltd | Wholesale & retail | 2021 |
| Throckley Timber Ltd | Wholesale & retail | 2023 |
| Thrty Ltd | Information & communication | 2021 |
| Thrunton Brickworks Management Company Limited | Real estate | 2025 |
| THS Inspection Services Ltd | Professional & scientific | 2014 |
| THS Retrofit Solutions Ltd | Professional & scientific | 2021 |
| Thunder Rugby Limited | Arts & recreation | 2009 |
| Thunderveil Limited | Information & communication | 2024 |
| Thurston Parfitt Limited | Professional & scientific | 1967 |
| TI Geosciences Ltd | Professional & scientific | 2008 |
| Tias Properties 2 Ltd | Real estate | 2018 |
| Tias Properties Limited | Households | 2015 |
| Tiba Tempeh Ltd | Manufacturing | 2019 |
| Tiberius Security Systems Ltd | Administrative & support | 2023 |
| Ticbox Limited | Information & communication | 2016 |
| Tick Finance Ltd | Wholesale & retail | 2011 |
| Tidal Wind Ltd | Construction | 2025 |
| Tidalgen Limited | Manufacturing | 2021 |
| Tide & Time Limited | Professional & scientific | 2020 |
| Tide Mechanical Services Limited | Construction | 2007 |
| Tide PUB Co Ltd | Hospitality | 2023 |
| Tier One Capital Financial Services Limited | Financial services | 2023 |
| Tier One Capital FM Limited | Financial services | 2023 |
| Tier One Capital Holdings Limited | Financial services | 2023 |
| Tier One Capital Ltd | Financial services | 2012 |
| Tier One Capital Wealth Management Limited | Financial services | 2005 |
| Tife Morrison Healthcare Ltd | Health & social care | 2025 |
| TIG Accountants Limited | Professional & scientific | 2023 |
| TIG Corporate Finance Limited | Professional & scientific | 2015 |
| TIG Group Holdings Limited | Financial services | 2023 |
| Tiger Hornsby Events Ltd. | Hospitality | 2014 |
| Tiger Lifting UK Limited | Manufacturing | 2011 |
| Tiger T Estates Limited | Real estate | 2016 |
| TIGERLILY54 Limited | Administrative & support | 2011 |
| Tighnabruaich Holdings Limited | Real estate | 2017 |
| TIK TOK Property Developments Ltd | Real estate | 2020 |
| Tikhal Ltd | Real estate | 2025 |
| Tikka Tikki RS Limited | Hospitality | 2025 |
| Tildist Realisations Limited | Wholesale & retail | 2020 |
| Tilemaster Ponteland Ltd | Other services | 2018 |
| Tiles Harbour Limited | Construction | 2024 |
| Tilewise NE Ltd | Wholesale & retail | 2021 |
| Tilia Lime Ltd | Hospitality | 2023 |
| Tiling Projects International Ltd | Construction | 2025 |
| Till Services Limited | Professional & scientific | 2006 |
| Tilley Sports Management Limited | Professional & scientific | 2009 |
| Tilly Magic Training Ltd | Other services | 2012 |
| Tilted Frame CIC | Education | 2024 |